Refer to Japanese Patent Laid-open No. 2005-173646.
As an example of information to be recorded on a recording medium in the form of a sheet, a one-dimensional code or a two-dimensional code represented by a bar code, a QR code, a dot code and so forth are available. However, in information recording media on which such codes are recorded, the amount of information which can be recorded per unit area is as small as approximately several tens to several kilo bites. This is because there is a physical limit to a recording resolution of density printing of a mere image.
Further, as another recording medium in the form of a sheet, also a hologram recording medium is known on which various data are recorded in the form of interference fringes using object light and reference light. Also it is known that the hologram recording medium can increase the recording density significantly thereby to allow remarkable increase of the recording capacity. Thus, it is considered that the hologram recording medium is suitable for use, for example, as a great capacity storage medium for computer data, AV (Audio-Visual) content data and so forth.
In order to record data on the hologram recording medium, the data are imaged as two-dimensional page data. Then, the imaged data are displayed on a liquid crystal display panel or the like, and light transmitted through the liquid crystal display panel is irradiated as object light, that is, object light which is to form an image of the two-dimensional page data, on the hologram recording medium. Further, reference light is irradiated on the hologram recording medium from a predetermined angle. At this time, interference fringes generated by the object light and reference light are recorded as one element hologram in the form of dots, rectangles or the like. In other words, one element hologram has data of one two-dimensional page recorded thereon.